Cryotherapy has numerous applications. For example, cryoprobes are used for the destruction of diseased tissue, the taking of tissue samples and/or for the removal of foreign objects. Furthermore, the applied cold can be used to stop hemorrhaging or prevent disadvantageous tissue changes.
In cryotherapy, in particular in cryosurgery, cold is frequently applied by means of a probe in order to achieve a healing effect.
Various methods exist for cooling the instrument, i.e., the cryoprobe. Frequently, the Joule-Thomson effect is utilized. In this case, a fluid, in particular a gas, is expanded near the application site via a nozzle in an expansion chamber, where the fluid experiences a temperature change. Among other things, the cooling capacity is a function of the temperature difference existing at the site of expansion. In order to ensure an effective cooling of the instrument it is necessary to discharge the expanded gas from the expansion chamber without causing any unwanted back-pressure.
In practice, there is a difference between cryoprobes with front pressure regulation and rear pressure regulation. Usually, a cryoprobe comprises a feed line and a return line. The feed line is always configured to be pressure-stable, but there are cryoprobes having a return line that are not pressure-stable. Front pressure regulation is used for adjusting the cooling capacity of such cryoprobes. In this case, the pressure is adjusted in the supply, depending on the desired cooling capacity. The return line has an essentially atmospheric pressure. In rear pressure regulation, the cooling capacity is regulated by the pressure in the return line at constant pressure in the fed line.
Considering probes comprising return lines that are not pressure-stable (front pressure regulation), there is a difference between open (open fluid cooling) and closed systems. In open systems, the fluid is discharged—due to expansion—either indirectly or directly to the environment. A return inside the instrument does not occur or occurs only conditionally. Some of the fluid is discharged into the organ or taken in by the endoscope. However, in conjunction with this, it must be taken into consideration that—for the safety of personnel—it must be ensured that only minimal amounts of fluid escape into the operating room while an operation is being performed.
A supply system for cryoprobes with a feed line and a return line, to which cryoprobes with front pressure regulation as well cryoprobes with rear pressure regulation can be connected, has been known from German publication DE 10 2006 003 571 A1. It is desirable that cryoprobes with open systems also can be connected to such a supply system.
Furthermore, it is an extreme problem that, considering such open systems, there is no possibility of detecting occlusions in the feed line, a functional failure of the pressure adjustment device or any excess pressure building in the systems. In such cases, this can result in damage to the instrument or also danger to the patient or user. Consequently, it is desirable that an overpressure protection or an overpressure safety feature be provided even for open cryoprobes or cryoprobes disposed for open fluid cooling.